Blower Motor Replacement - W124 Chassis

Here's a page I threw together in a few minutes to illustrate replacing the W124 blower motor.  This is intended for do-it-yourselfers of average skill like myself.  Eventually I'll spiff this site up and make it attractive.

DISCLAIMER:  I'm not a professional mechanic, just a do-it-yourselfer.  This article probably has some of the steps out of order, omitted, or performed incorrectly.  All I know is it worked for me.  If it works for you too, great!  If not, I cannot be held responsible.  PROCEED AT YOUR OWN RISK.

IMPORTANT NOTE:  My particular car is a 1990 300CE with the Behr air conditioning unit.  I ordered the bare replacement motor ($99.00 without squirrel cages) from German Star and it dropped right in.  I've read posts by W124 owners who have had assorted problems installing aftermarket replacement motors.  So as the saying goes, your mileage may vary.  I strongly recommend doing some research before you jump into doing this job.  If you decide to go for it, proceed with caution.  If in doubt, STOP and consult an expert and/or a shop manual.  I strongly recommend purchasing the CD-ROM-based Mercedes shop manual as I found it quite helpful while performing this repair.

Moving right along...

First, remove the wiper arm from the wiper assembly.  This lessens the chance of cracking the windshield and makes it easier to get the wiper motor assembly out.  For that matter, I'm not sure you could get it out with the arm attached. Just trust me on this one. :-)

Raise the wiper arm until it is fully extended.  Remove the trim piece covering the set screw.

Remove the allen head set screw, then slide the arm off the shaft. As you can see in the photo, you may want to use a screwdriver to relieve enough tension for the arm to slide off.

Next, raise the hood and remove the two plastic trim pieces that cover the lower edge of the windshield. They're held in by spring clips and should only require a firm tug straight out.

Now remove the eight screws along the bottom of the windshield (see crude-but-effective red arrows). Note that the outer two are not visible in this photo.  Also remove the four tiny screws securing the rubber seal surrounding the wiper motor assembly.  This also would be a good time to pull the weather stripping out of the way.

The outer plastic trim sections are joined to the center section with these white clips - one on each side of the car. Pull them straight out toward the front of the car, then separate the pieces.  Be careful not to let them get away from you and fall into the car's nether regions!  I also removed the plastic piece behind the battery that covers the ECM, but this may not have been necessary.

Next remove the foam-covered trim directly behind the cam cover.  There are two large, plastic thumscrews securing it to the front of the box containing the blower motor.  Hopefully the trim in your car is in better shape than mine.  This photo also shows a decent view of the weather strips that have to be partially removed during disassembly.
 

Remove the front part of the grille by releasing the two tabs on the outer edges that connect it to the adjacent trim panels.

Remove two screws that fasten the grille to the top of the box, then carefully remove the grille.

Now the wiper assembly is accessible.  Remove the four 10-millimeter nuts and then carefully lift the assembly out of the car.

Okay, I didn't take any photos of removing the top of the box from the blower motor.  It's very straightforward - just pop the clips loose and carefully remove the top of the box.  To remove the motor, unclip the metal strap from its fastening point in the back, then remove the two wires from their terminals.  BE CAREFUL removing the motor assembly!  The squirrel cages are fairly delicate.  If you mess these up, you're looking at a $300.00 fan assembly instead of a $100.00 bare motor.

To ensure proper balance, mark the squirrel cages before removing them so that they can be installed on the new motor in their original alignment.  While it might not make a difference, I was careful to put the cages on the same side of the new motor as they were the original motor, then rotated the two fans into their original alignment using my marks.  Proper balance is important or your motor could wear out prematurely.

The most tricky part of the job is removing the squirrel cages from the old motor.  My friendly neighborhood Auto Zone was kind enough to lend me this gear puller for a mere $40.00 deposit.  There may be a better way to remove the squirrel cages, but this was the safest I could think of.  The key here is patience.  Work slowly!  Like I said before, it's going to cost you a fortune if these babies get broken.  I used a little WD-40 to help move things along.  If you do the same, be sure to clean off all the WD-40 before you put them on the new motor.  The squirrel cages will slide onto the spindle of the new motor fairly easily.  I wrapped a rag around one end of the shaft and clamped it in some vise grips to hold it still.  Then I pressed the squirrel cage onto the opposite end of the shaft and twisted back-and-forth until it was close to the correct position.

Note that the squirrel cages must be located in the proper position along the length of the spindle in order to clear the sides of the box.  It took me three or four test fittings to get everything tweaked just right.  Make sure the motor fits securely into the mounting bracket and check to make sure the squirrel cages rotate without interference.  Once everything looks good, fasten the motor with the metal band, plug in the power connectors, and put the top back on the box.  Turn on the ignition switch, select the "normal" climate control setting, and select high fan speed.  If you get strong airflow to the correct vents, congratulations!  Now you can finish the reassembly.

If you hear the fan but there is little or no airflow, check to make sure you don't have the squirrel cages facing the wrong direction.

Please Email any questions, corrections, or additions to Jay Slabotsky at rocker151@hotmail.com.